During experiments using antisense oligodeoxynucleotides to define an autocrine role for IGF-I in WI-38 cells, a human fetal lung cell line, we discovered a novel RNA that we call BB1. BB1 appears important to cellular proliferation, because when BB1 antisense oligodeoxynucleotides (oligos) hybridize with BB1 RNA in vivo, BB1 translation is apparently blocked and DNA synthesis is reduced to 10% of control values. We have cloned and sequenced a 2251 base pair BB1 cDNA, corresponding to the 2.3 kilobase RNA seen in Northern analyses. We postulate that the human BB1 RNA encodes a 6,270 dalton protein that is essential for traversal of the mammalian cell cycle. In this application we propose to determine BB1's function in the cell cycle, to determine BB1 action(s) in lung organogenesis, to investigate the regulation of BB1 protein synthesis, and to characterize BB1 gene structure. Specifically, we propose to synthesize and purify BB1 protein for use in making antibodies for use as probes to delineate BB1's function in the cell cycle. We will use BB1 antisense oligos in fetal rat lung organ explant cultures and examine the effect that blocking BB1 translation has an airway branching and lung morphogenesis. As an alternative approach to define BB1 function, we will overexpress BB1 protein in vitro using a fusion of the BB1 cDNA and the mouse metallothionein promoter and examine alterations of cell cycle (measures will include studies of growth rate, S phase duration, etc.). BB1 translation and translational regulation will also be studied in stably transfected cells. Lastly, we propose to isolate and characterize the BB1 gene(s) including its flanking regions. To define its coding regions, we will use the full length BB1 cDNA to map the exonic structure. Promoter and regulatory sequences will be determined by stably transfecting BHK or GM10 cells with fusion constructs made by fusing 5' flanking genomic DNA fragments to a chloramphenicol acetyl transferase (CAT) reporter gene and assaying for stimulations of CAT activity.